> [The main advantage of TXL is that it has a lot of I/O and tree> building as part of the languge, whereas you have to implement> them yourself if you used a yacc parser. -John]

Right. The determination and modeling of the semantical structure
(AST...), and the transformation of that structure, are different tasks,
which in traditional approaches require different programming languages
or libraries. IMO it's a big advantage, to have everything in a single
language. It's less important when very different techniques are
required, like in general-purpose multi-target compilers, which can be
separated into multiple, widely independent phases.